dextron II vs type f

Discussion in 'Canadian Daves JustKDX' started by sr5bidder, Feb 15, 2012.



  1. sr5bidder

    sr5bidder Rookie DRN Member

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    anyone tried dextron II I have just aquired 4 qt for free and was thinking of giving it a try as I am unemployed and it is free.

    My thoughts: all auto transmissions have clutch packs soooo... and dexron is a newer generation of tranny fluid.

    numbskull testing has found they feel similar between the fingers....sooo has anyone tried or am i on a new frontier?


  2. duncanstives

    duncanstives Member DRN Member

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    I put Dexron III in mine since I heard it was better than using gear oil. Havn't really noticed a difference compared to whatever was in there (appeared to be oil of some sort... LOL). Shifts seem quicker and more "snappy" (if that makes any sense) but it could easily be the new shifter (slightly different shape) or the fact that I adjusted the clutch cable a bit.

    I will say this: I filled it, rode it for awhile and changed it again per instructions I found on the internet... There was nothing alarming looking in it when I took it out (like metal flakes) so I guess it does a decent job of lubrication.

    I'd guess dextron II is similar to III as far as these things are concerned... I'd run it.
  3. sr5bidder

    sr5bidder Rookie DRN Member

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    I just found a service bulletin from KTM tellig the techs to use dextron in thier 50's
    Motorex ATF Super (Dexron II Gear Oil)
  4. ericmiles

    ericmiles Rookie DRN Member

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    Type F had no friction modifers.
    Dexron (and Mercon and old type A) has friction modifers.

    Friction modifiers change the shift "firmness" and are specified depending upon the clutch and band friction materials used in the manufacture of the transmission. The original GM Hydramatic had metal plates and used motor oil. In the late 1940's they switched to a fiber friction material and invented a fluid with the correct frictional properties, Type A. The various Dexron formulas are backward compatible to 1949!

    Also you can see this page and look at the second FAQ question relative to Type F / Dextron http://www.valvoline.com/faqs/system-fluids/automatic-transmission-fluid/

    I don't see how it could harm anything. It should lubricate fine. Worse thing I could think of is that the so-called friction modifiers might make it too slippery or coat the plates resulting in clutch slippage??? I use ATF type F just because thats what I started with and it worked...if I had started with Dextron II or III then I would probably say that worked :)
  5. mudpack

    mudpack Rookie DRN Member

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    Good info, eric.
    Now, my question is this: In what way do the "friction modifiers(FM)" change friction characteristics?
    Does a FM make the oil MORE slippery (less friction), or does the FM make the oil LESS slippery (more friction)?

    Inquiring minds want to know.

    As far as Dextron being okay to use in a multiplate clutch/transmission, yes, it is fine. I know many riders who have used it for decades without ill effect.
  6. ericmiles

    ericmiles Rookie DRN Member

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    hmmm...good question. I assumed more slippery when I first researched it, since it is oil we are talking about here, but we are talking about interaction with plates that need to GRAB...I was puzzled....so for my lunch time entertainment I used my good friend Google.
    After lots of reading I found a guys post over at bobistheoilguy.com that made sense to me...your mileage may vary...here is a copy and paste of Pete2k_Z28 post:
    Re: What do Friction Modifiers Do?
    Perhaps I can lend some insight to the topic?

    Before you can understand how friction modifiers function, it is important to understand how "wet" clutches perform.

    In a wet clutch arrangement, there are three stages of engagement. During the first stage, the clutch is not in contact with the pressure plate or other metal plate. We will use an automatic transmission torque converter as an example. Anyone who has driven auto trans cars with lockup torque converters for a while has probably experienced a phenomenon known as "lockup shudder" or "torque converter shudder". Shudder is caused during torque converter clutch lockup by burnt fluid or fluid wich has exhausted all of it's friction modifers. The result is a chattering feeling when the torque converter goes into lockup mode. I will now attempt to explain the physics of wet clutch engagement.

    As I have already mentioned, during the first stage the clutch is not in contact with it's mating surface. The fluid itself, however, is acting as a viscous coupling, causing a partial engagement. A side effect of this is heat, and I believe you all know that heat is the killer of automotive oils.

    The second stage is very simlar to the first. At this point the clutch is very close, possible within thousandths of an inch, from it's mating surface. The viscous coupling is now more effective, but the pressure and shear load on the fluid are also higher, and the result is increased heat.

    During the third stage, the clutch actually contacts it's mating surface and positive engagement is reached. The shear load of the fluid has been overcome and has either extruded itself outside of the clutch material or, depending on the application, has partly or entirely extruded itself through a porous friction material, thus exiting the engagement area of the clutch.

    Now that we have an understanging of wet clutch engagement, lets see how that plays out in the real world. If a fluid has lost a substantial amount of the friction modifier, the shear of the fluid will be inconsistant accross the engagement surface and the clutch will briefly alternate between full engagement (stage 3) and viscous engagement (stage 2). The as power through the assembly varies, wich is connected in our case to a vehicle that we are inside of, a bucking of sorts is perceptable to it's occupants as power transmitted to the wheels is momentarely interrupted and regained.

    In an application like a limited slip rear end, similar phenomena occur but in a slightly different manner. Because the clutch plates are constantly loaded with heavy springs, in theory they should always remain in stage 3 of lockup. If that were the case however, they would never slip. So the purpose of a friction modifier in a rear end is to ensure that the transition from S3 to S2 and back again during cornering etc. is smoothe. Therefor chatter occurs in much the same way it does in our torque converter clutch scenerio.

    So the answer to your question if friction modifiers enhance friction or reduce it? The answer is there is no answer. Depending on what the application calls for and how it is engineered, they can do either. So as Alex said, it does just that; modifies friction.

    And now hopefully you will understand why and how as well

    Pete

    AND AS THE NEXT POSTER SAID:
    Good explanation, Pete. I guess that's why they're called friction "modifiers", instead of "friction reducers" or "friction enhancers".
  7. sr5bidder

    sr5bidder Rookie DRN Member

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    Nice find I changed the tanny fluid today and used the dextron III and it seems no differnt than the type f after a fresh change ..nuetral is easy again and shifting is nice and smooth and easy
  8. mudpack

    mudpack Rookie DRN Member

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    Thanks, Eric. :cool:
  9. motopsycho87

    motopsycho87 Rookie DRN Member

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    If you are going to se ATF, use TYPE G, it is an evolved form of type F, still with no friction modifiers.

    That being said, I did an enduro with ATF in the bike yesterday and the gear changes were HORRIBLE. The second it got hot it refused to play ball. But somehow neutral was really easy to find... :coocoo:



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